Refrigerating machine



July 7, 1936. H. w. BROWN -RE'FRIGERATING MACHINE Ihm.

Filed Dec. 5

'fill/lll',

fill] Sw /o Inventor: Harold W Br'ow'n, bg CL:

His Attorney.

Patented July 7V, i936 REFRIGERATING' MACHINE Harold W.Brown,Schenectady, N. Y., assignor to General Electric Company, a corporationof New York Application December 5.1934, serial'No. '156,109

7 claims. (ci. isz-13er UNITED STATES PATENT -GFFICE My inventionrelates to refrigerating machines of the type in which a gaseousrefrigerant is compressed, and cooled Without liquefaction, and is thenexpanded to produce refrigeration.

Refrigerating machines of the type in which a gaseous refrigerant, suchas air, is circulated without liquefaction may be constructed utilizinga compressor in which the gaseous refrigerant is compressed at one endof the stroke and ex,-

panded at theu other end, the compressed gas betermed a wattlesscompressor. The operation of this compressor tends to equalize thepressures and temperatures in the high and low temperature circuits, anda second power compressor is provided for pumping refrigerant from thelow pressure circuit to the high pressure circuitin order to maintainthe desired pressure diierence.

An object'of my invention is to provide an im-v proved arrangement foractuating or driving a wattless compressor employed in arefrigeratingmachine of the type in which a gaseous refrigerant iscirculated without liquefaction.

Further objects and advantages of `my invention will become apparent asthe following description proceeds, and the features of novelty whichycharacterize my invention will be pointed -out with particularity inthe claims annexed to and forming a part of this specification.

Fora better understanding of my invention, reference may be had to theaccompanying draw- 4Q ling, the single iigure of which illustratesdiagrammatically a refrigerating machine embodying my invention.

Referring now to the drawing, I have shown a refrigerating machineincluding a wattless compressor I 0, connected with a high pressurecircuit comprising an air or water cooled coil II and a` scavenging .fanI2, and connected with a low pressure circuit comprising a refrigeratingcoil I3 and a scavenging fan I 4. A'I'he wattless compressor I0 is ofthe double-acting type and i comprises a body l5 having cylinders I6 and[6a communicating with each other at both ends vthrough clearance spacesI1 and I8. Within the cylinders I8 and IGa arevarranged pistons I9 andI9a,`which are connected by a yoke 20, so that they reciprocate inuniso'n, the yoke moving into the slot 20a when the pistons move to theleft. The cylinder I6 is provided with intake ports 2I and 22communicating with the high pressure circuit, and with an intake port 23arranged midway between the ports 2l and 22 and communicating with thelow pressure circuit. The cylinder Ilia is provided with exhaust ports2Ia and 22a communicating with the high pressure circuit and with anexhaust port 23a arranged midway between the ports 2 Ia and 22a andcommunicating with the low pressure circuit. These ports are annularexcept for the portions of the cylinderv walls left to provide therequisite strength. The pistons I9 and I9@ are provided with passages 24andl 24a respectively at theI left ends thereof right ends thereof.These passages open at the sides of the pistons and are arranged toregister with their respective cylinder ports when the pistons are nearthe endof their stroke, and thereby provide a` passage from theintakeports in and with passages 25 and 25a respectively at the cylinderI6 through theclearance spaces to the.v

exhaust ports in the cylinder IBa. t l n During operationvof therefrigerating machine shown when the pistons I9 and Isa. are moved .to

their extreme left-hand positions, ythe passages 24 and 24a willprovidevcommunicationfbetween t i A the clearance space I1 and the highpressure ports.,v

2I and 2 I a, and the passages 25A andq25a will-profvide communicationbetweenthe clearance space I8 and the low pressure .ports 23fand 23a.-The gas, which has been compressed in the clearance i space I1 byoperation of the pistons, will; now; be

driven out through, the port `2Iaby operation of the scavenging fan-I 2,which will force air cooled in the coil II through` theportZIr and. intothe clearance space I'I. This Path of the gas in the high pressurecircuit is indicated byA arrows. By this scavenging operation the hotcompressed gas is displaced by gas cooled in the coil II at subt lowpressure circuit is indicated by arrows. The

by cooler gas, a greater weight of gas is taken from the high pressurecircuit than is added thereto, and a greater weight of gas is added tothe low pressure circuit than is taken therefrom during the scavengingoperation. In order to overcome this eilect and prevent the gradualequalization of the pressures in the high and low pressure circuits, acompressor 26 is provided to pump gas from a connection 21 on the warmside of the coil I3 of the low pressure circuit to a connection 28 onthe warm side of the coil II of the high pressure circuit. Thiscompressor is hereafter termed the power compressor.

In the operation of the compressor I0 the pistons I9 and I9areciprocate. The gas is compressed at one end of the pistons, expandedat the other end thereof, and the pressures in the low and high pressurecircuits are maintained substantially constant, so that the net workdone on the gas is zero. -The power input to the wattless compressor IIl, therefore, need supply only the friction losses in the compressor inorder to keep the pistons in operation. It is evident that the pistonswill have a natural period of oscillation under the action of the gaswithin the cylinder somewhat like that of a spring, there being adifferential of zero pressure between the ends of the pistons at themiddle of the stroke. The variation from the simple harmonic motion,such as that of an oscillating spring is due to the fact that thepressure does not change during the opening of the ports at the ends ofthe stroke,

and since the ports are open for an appreciable time the restoring forceis constant for this time vand does not act to produce simple harmonicmotion.

In accordance with my invention I avoid the necessity ofvproviding aseparate driving device for moving the pistons of the wattlesscompressor III. I accomplish this object by increasing the capacity ofthe power compressor 26 above that necessary to maintain a balancebetween the low pressure and high pressure circuits, by an amountsuiilcient to supply the friction losses within the wattless compressor.Furthermore, since the pistons of the wattless compresser normally cometo rest in midposition, this arrangement provides for setting thepistons in motion during starting of the machine.

Referring again to the drawing, it will be noted that the pistons I9 andI8a are secured together by the yoke 2li, and are free to oscillate inunison within the cylinders I6 and |60.. These pistons are shown intheir mid-positions, which is their normal position when therefrigerating machine is not operating, because the pressures in theclearance spaces I1 and I8 are the same when the pistons are in theirmid-position. Obviously it is impossible to start the pistons byapplication of pressure at the cylinder ports -since the ports are allclosed when the pistons are in mid-position. In order to set the pistonsin motion upon starting of the refrigerating machine, I provide aconduit 29 having therein a normally closed valve 30 which in its openposition provides communication between the high pressure circuit andthe clearance space I1 at one end of the compressor, and a conduit 3|having therein a normally closed valve 32 which in its open positionprovides communication between the low pressure circuit and theclearance space I8 at th other end of the compressor.

In order to set the pistons I9 and I9a in motion, the power compressor26 is started thereby v When the ports 2| and 2Ia open, this pressureproducing a pressure difference between the high and low pressurecircuits. When the valves 30 and 32 are opened, the pistons are forcedto thel right since the pressure within the space I1 is greater thanwithin the space I8. At the end of 5 the stroke the space I8 is placedin communication with the high pressure circuit through the passages 25and 25a in the piston and the space I1 is placed in communication withthe low pressure circuit through the passages 24 and 24a and furthermotion of the pistons will be cushioned and arrested. If the valves 30and 32 are now closed, the space I8 being then open only to the highpressure circuit and the space I1 being open only to the low pressurecircuit, the pistons will move back and will continue to oscillate attheir natural period provided the friction losses are overcome. Iprovide an automatic arrangement for operating the valves 30 and 32 onlyduring starting, which will be described 20 later, the valves beingclosed as soon as the ports open at the end of the first startingstroke.

In order to overcome the friction losses of the compressor during itsoperation after it is started, and thereby to make it possible for thepistons 25 to oscillate at their natural period, I increase the capacityof the compressor 26 over that which would be necessary to maintain abalance in the system if the wattless compressor were driven by anexternal device. This increased pressure 30 is then available to forcethe pistons I9 and I9a to the end of their stroke against friction.During operation of the compressor, when the pistons reach their extremepositions to the left the high pressure ports 2l and 2Ia open and thepressure 3.5 in the space I1 becomes that of the high pressure circuit.The pressure in the space I1 is greater than that produced by thevcompressor I0 because of the additional pressure produced by thecompressor 26. This additional pressure produced by the compressor 26while the ports 2| and 2Ia are open, being greater than that necessaryto compress the gas on the right end of the pistons in the space I8 issuiilcient to overcome friction and move the pistons to the right untilthe passages 24 and 24a register with the low pressure ports 23 and 23arespectively. Since additional pressure was necessary to move thepistons against friction to this extreme right position, the pressurewithin the space I1 is greater than the pressure within the low pressurecircuit, and some of the expanded gas will ow into the low pressurecircuit to equalize the pressures. On the return stroke to the leftthere is then less gas in the space I1 than on the expansion stroke, andwhen the pistons have reached their extreme left position thecoinpressed gas within the space I1 will be at a pressure less than thatof the high pressure circuit.

will be equalized at the pressure of the high pressure circuit and theforegoing cycle will be repeated, the operation at the two ends of thepistons being the same. It is apparent, therefore, that the compressorI0 will continue to operate 65 as long as a suiilcient differential. ofpressure is maintained by operation of the power compressor 26 to supplythe friction losses.

In order to obtain quick and reliable starting of the pistons I9 and I9aat the beginning 70 of the operation of the refrigerating machine,

I provide an automatic arrangement for operating the valves 30 and 32including an electrical control circuit associated with an electricmotor 33 or other power device utilized to drive the 75 compressor 26.The electric `motor 33 drives the compressor through a connecting rod 34and piston rod 35, power being supplied to the motor 33 through leads 36and 31 connected toa sluitable source of supply through a switch 38. Thevalves 30 and 32 are provided with operating arms 39 and springs 40connected to the arms 39 for biasing the valves to their closed positionand with solenoids including movable armatures 4I pivoted to the arms 39and coils 42 for moving the armatures against the force of the springs40 to open the valves. 'I'he coils 42 are connected in parallel acrossthe motor leads 36 and 31, a normally open relay 43 being provided inone side of the solenoid circuit. When it is desired to start thecompressor I0 the relay 43 is closed against a latch 44, so that whenthe switch 38 is closed to start the motor 33 the solenoid coils 42 willbe energized and will open the valves 30 and 32. When the valves areopen the pistons I9 and 19a. will move to the right in the mannerdescribed above and the clearance space I1 will be placed incommunication with the low pressure circuit of the refrigerating machinethrough ports 23 and 23a. Since the space l1 is in communication withthe high pressure circuit through the conduit 29 and valve 3|), therewill be a rush of gas from the space I1 through the passages 24 and 24a.into the low pressure circuit. In order to utilize this rush of gas toclose the valves 30 and 32, I provide a contact making check valve 45 ina conduit 46 which connects the scavenging fan I4 and the low pressurethe relay 43 will be tripped, thereby deenergizing the coils 42 andclosing the valves 30 and 32. When the valves have been closed normaloperation of the compressor continues, as long as the compressor 26 ismaintained in operation to produce the necessary pressure differencebetween the high and low pressure circuits.

From the foregoing itis apparent that I have provided a simple andimproved arrangement for starting and driving a refrigerating machine ofthe type in which the gaseous refrigerant is circulated withoutliquefaction and which employs a wattless compressor.

While I have shown my invention as applied to a particular form ofrefrigerating machine,

`other applications will readily be apparent to those skilled in theart. I do not, therefore, desire my invention to be limited to theparticular embodiment shown and described, and I intend in theaccompanying claims to cover all modications within the spirit and scopeof my invention.

What I claim as new and desire to secure' by Letters Patent of theUnited States, is

1. A refrigerating machine of the type in which a gaseous refrigerant iscirculated without liquefaction including a closed system comprising ahigh pressure refrigerant circuit and a low pressure refrigerantcircuit, means including a wattless compressor having a cylindercommunicating with said circuits and a piston freely movable in saidcylinder for compressing regrigerant received from said low pressurecircuit and for expanding refrigerant received from said high pressurecircuit, scavenging means for forcing refrigerant compressed in saidcylinder into said high pressure circuit, scavenging means for forcingrefrigerant expanded in said cylinder into said low pressure circuit,and means including a power compressor connecting said circuits forpumping refrigerant from said low pressure circuit to said high pressurecircuit and for actuating said piston.

2. A refrigerating machine of the type in in which a gaseous refrigerantis circulated without liquefaction including a closed system comprisinga high pressure refrigerant circuit and a low pressure refrigerantcircuit, means including a wattless compressor having a cylinder com-ymunicating with said circuits and a piston freely movable in saidcylinder for compressing refrigerant received from said low pressurecircuit and for expanding refrigerant received from said high pressurecircuit, scavenging means for forcing refrigerant compressed in saidcylinder into said high pressure circuit, scavenging vmeans for forcingrefrigerant expanded in said cylinder into said low pressure circuit,means arranged in said high pressure circuit for cooling compressed gasdischarged from said cylinder, means utilizing the heat absorbingcapacity of the expanded gas discharged from said cylinder for producingrefrigeration, and means including a power compressor connecting saidcircuits for pumping refrigerant from said low pressure circuit to saidhigh pressure circuit and for actuating said piston.

3. A refrigerating machine of the type in which a gaseous refrigerant iscirculated without liquefaction including a closed system comprising ahigh pressure refrigerant circuit and a low pressure refrigerantcircuit, means including a Wattless compressor having a cylindercommunicating with said circuits and a piston freely movable in saidcylinder for compressing refrigerant received from said low pressurecircuit and for expanding refrigerant received from said high pressurecircuit, scavenging means for forcing refrigerant compressed in saidcylinder into said high pressure circuit, scavenging means for forcingrefrigerant expanded in said lcylinder into said low pressure circuit,means including a power compressor connecting said circuits for pumpingrefrigerant from said low pressure circuit to said high pressure circuitand for actuating .said piston, and means utilizing compressed gas forinitially producing motion of said piston to start said wattlesscompressor.

4. A refrigerating machine of the type in which a gaseous refrigerant iscirculated without liquefaction including a closed system comprising ahigh pressure refrigerant circuit and a low pressure refrigerantcircuit, means including a wattless compressor having a cylindercommunicating with saidcircuits and a piston freely movable in saidcylinder for compressing refrigerant received from said low pressurecircuit and for expanding refrigerant received from said high pressurecircuit, scavenging means for forcing refrigerant` circuit for initiallyproducing motion of said piston to start said wattless compressor.

5. A refrigerating machine of the type in which a gaseous refrigerant iscirculated without liquefaction including a closed system comprising ahigh pressure refrigerant circuit and a low pressure refrigerantcircuit, means including a wattless compressor having a cylindercommunicating with said circuits and a piston freely movable in saidcylinder for compressing refrigerant received from said low pressurecircuit and for expanding refrigerant received from said high pressurecircuit, scavenging means for forcing refrigerant compressed in saidcylinder into said high pressure circuit, scavenging means for forcingrefrigerant expanded in said cylinder into said low pressure circuit,means including a power compressor connecting said circuits for pumpingrefrigerant from said low pressure circuit to said high pressure circuitand for actuating said piston, a conduit connecting said cylinder on oneside of said piston with said high pressure circuit, a conduitconnecting said cylinder on the other side of said piston with said lowpressure circuit, valves in said conduits, means operable upon startingof said compressor for opening said valves and for initially producingmotion of said piston to start said Wattless compressor, and meansresponsive to operation of said piston for closing said valves.

6. A refrigerating machine of the type in which a gaseous refrigerant iscirculated without liquefaction including a closed system comprising ahigh pressure refrigerant circuit and a low pressure refrigerantcircuit, means including a wattless compressor having a cylindercommunicating with said circuits and a piston freely movable in saidcylinder for compressing refrigerant received from said low pressurecircuit and for expanding refrigerant received from said high pressurecircuit, scavenging means for forcing refrigerant compressed-in saidcylinder into'said high pressure circuit, scavenging means for forcingrefrigerant expanded in said cylinder into said low pressure circuit,means ncluding a power 5 compressor connecting said circuits for pumpingrefrigerant from said low pressure circuit to said high pressure circuitand for actuating said piston, and means dependent upon starting of saidpower compressor for supplying gas from said 10 high pressure circuit tosaid cylinder for starting said wattless compressor.

7, A refrigerating machine of the type in which a gaseous refrigerant iscirculated Without liquefaction, including a closed system comprising a15 high pressure refrigerant circuit and a low pressure refrigerantcircuit, means including a wattless compressor having a cylindercommunicating with said circuits and a piston freely movable in saidcylinder for compressing refrigerant received 20 from said low pressurecircuit and for expanding refrigerant received from said high pressurecircuit, scavenging means for forcing refrigerant compressed in saidcylinder into said high pressure circuit, scavenging means for forcingrefrigerant 'expanded in said cylinder into said low pressure circuit,means including a power compressor connecting said circuits for pumpingre frigerant from said low pressure circuit to said high pressurecircuit and for actuating said piston, means dependent upon startingsaid power compressor for supplying gas from said high pressure circuitto said cylinder for starting said wattless compressor, and meansdependent upon the ow of gas in said low pressure circuit for cuttingoif the flow of gas from said high pressure circuit to said cylinderthrough said last mentioned means.

HAROLD w. BRowN.- 4o

